The invention relates generally to a windshield wiper arrangements particularly for motor vehicles, and more specifically to drive units having changing length push rods.
An arrangement having a part, which prevents blocking of or damage to the windshield wiper unit, installed in the force-transfer path from the motor to the wiper blade, is known from the U.S. Pat. No. 3,336,619. Here, the lever leading to a wiper bearing is made in two pieces and an arrangement is created in between which allows change in length of the lever when the wiper is impeded. This arrangement includes two tubes, which are inserted into one another and are elastically connected by a spring, and an additional safety bolt which limits the change in length to a maximum amount. To obtain a frictional connection for normal wiper operation, which connection can transfer the movement of the drive motor to the wiper bade and moreover is so rigid that no chattering occurs in the wiper blade, the spring must either be made rigid or installed in pretensioned manner. However, this necessitates very high blocking forces until the protective action occurs which results from the adjusting displacement of the spring. It is therefore possible for some parts of the windshield wiper unit to have already sustained damage by then. It is therefore difficult in this arrangement to achieve an acceptable compromise between rigid forced transfer and adequate tensile and compressive elasticity when the wiper blade is blocked.
The object of the invention is therefore, by means of an elastic push rod, to protect a windshield wiper unit from damage by blocking and at the same time to construct the push rod in such a way that absolute stability in every loading condition is achieved with few components. Moreover, the expense is to be reduced by using simple parts in mass production and to fully automatic manufacture, but with it being necessary to retain the simple adaptation to various windshield wiper units.
These and other objects of the invention are attained by providing a unique force responsive, varible length push rod between the motor and the windshield wiper for a windshield wiper unit. The force responsive, variable length push rod includes two members, one being connected at one end to the motor and the other being connected on end to the wiper blades. The other ends of the two members overlap each other with a space therebetween. Each member includes a plurality of lobes extending into the space between the members and an elastomer adheres to and fills the space between the plurality of lobes thereby forming the force responsive, variable length push rod. The lobes are of equal length and are formed to extend perpendicular from a base portion of each member, the base portion being parallel to each other in the overlap area. The lobe members are equally spaced along the axis of overlap from each other and from an adjacent interdigitized lobe of the other member. The lobes are formed by stamping the base portion and bending them perpendicular thereto leaving an opening. The lobe of the one member is centered on the opening of the opposed member. The base of the lobes for both members may be formed identical to each other and have distinctive lever portions welded thereto.
At the same time, the elastomer forms a volume which can be compressed or extended by the force initiation via the lobes. The fixed connection of the parts ensures an optimum, direct force transfer in wiper operation and moreover stability and guidance properties of the push rod subjected to additional loading. At the same time, because of the separation of the metal parts by the elastic connection, the vibrations and noise produced by the drive motor are absorbed. The elastomer, which can be extended or compressed from a certain loading lever, ensures that the excess movement of the drive side is compensated.
At the same time, the necessary loading magnitude from which compensation is necessary in the push rod can be introduced via the area of the lobes multiplied by their distance from one another and via the Shore hardness. The push rod, with simple changes, can thereby be adapted to every windshield wiper unit. The components are to be manufactured as a mass produced product and can also be assembled automatically to form the push rod.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment in accordance with the present invention.